Autonomic Nervous System

I. Divisions

A. Sympathetic

• fight or flight response

B. Parasympathetic

• rest and digestion

II. Involuntary Motor System

A. Autonomic vs. Somatic motor systems

1. Somatic

• voluntary

• direct synapse

• excitatory

2. Autonomic

• involuntary

• disynaptic (preganglion, postganglion)

• Excitatory and inhibitory

III General nerve pathways

A. Sympathetic

• Preganglion cell body – gray matter

• axons move through ventral root of spinal nerve

• synapse w/ postganglion at sympathetic chain ganglion

• axons of postganglions exit via

Spinal nerve

Sympathetic nerve

Exceptions: some pre do not synapse at symp chain

Splanchnic nerve

axons of preganglion exit Splanchnic nerve and

synapse at collateral ganglion w/post

Adrenal gland

preganglion synapses directly w/adrenal

B. Parasympathetic

• cell bodies of preganglion – brainstem (nuclei)

and sacral region of spinal cord

• axons move through cranial nerves

and through spinal nerves

• synapse w/ postganglion at ganglia near or in the target

IV. Signal transmission

A. Sympathetic

• Preganglion secretes Acetylcholine (Cholinergic)

• Postganglion – receptor = Nicotinic

• Postganglion secretes Norepinephrine (Adrenergic)

• Target (smooth muscle, cardiac, glands)

Receptor = Adrenergic (α,β)

Sweat Glands

• Preganglion secretes Acetylcholine

• Postganglion – nicotinic receptor

• Postganglion secretes Acetylcholine

• Sweat gland – muscarinic receptor

B. Parasympathetic

• Preganglion secretes Acetylcholine (Cholinergic)

• Postganglion – receptor = nicotinic

• Postganglion secretes Acetylcholine

• Target (Smooth muscle, heart, glands)

receptor = muscarinic

V. ANS generalized

A. Regulated

B. Excitatory and inhibitory

• depends on the target organ

C. Opposite effects

VI. Autonomic control

A. Cardiovascular function

• Sympathetic: Norepinephrine -

Increases cardiac muscle contractions

Increases blood pressure

• Parasympathetic: Acetylcholine

Decrease in cardiac output due to decrease in

calcium influx

B. Pupillary light reflex

1. Parasympathetic

• constricts pupil

2. Sympathetic

• Dilates pupil

C. Salivary glands

1. Sympathetic

• viscous secretion/ vasoconstriction of blood vessels

2. Parasympathetic

• watery secretion/ vasodilation of blood vessels